In western montana on several occasions a lobe of ice

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In western Montana, on several occasions, a lobe of ice created a temporary dam on the Clark Fork River that produced temporary lakes up to 1000 feet deep. The ice sheet began to rapidly melt about 13,000 years ago, depositing the unsorted glacial till sediment that the glaciers once carried. In eastern Washington, a series of colossal floods occurred as water trapped by the ice dams broke and ancient Lake Missoula was periodically released. There is evidence that walls of water as much as 900 feet high surged across Eastern Washington, eroding the landscape all the way down to the basalt bedrock.
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750 mya: ______________________________________________ 1100 mya: _____________________________________________ 550-250 mya: _______________________________________ _ 160 mya: _____________________ & ______________________ collide into North America (terrane accretion) 90 mya: _______________________________________________ 60-50 mya: ___________________________________________ & ____________________________________________ 40 mya: Cascadia subduction zone forms & Cascade Arc becomes active 17-6 mya: ______________________________________________ 14 mya: Current Cascade range begins to be uplifted 2 mya: continental glaciation begins, covering parts of WA ~6 times 20,000-11,000 yrs ago: ___________________________________ 15,000 yrs ago: _________________________________________ 13,000 yrs ago: _________________________________________ 700,000 yrs ago: ________________________________________ 1.8 TA CHECK_________________ Lab #8: Geology of Washington 113 In-Class Activities Activity 1: Geologic Timeline of Washington The purpose of this activity is to reconstruct Washington’s geologic history step by step using the information provided in this lab and your flip book. It is customary to list geologic events with the oldest event at the bottom and the most recent (youngest) at the top. More events have occurred in Washington’s geologic history than are discussed in this lab, but you only need to list the events included in this lab
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GEOLOGIC CROSS-SECTION OF WASHINGTON Olympic Mts. W E North Cascades Present day subducting Juan de Fuca plate CRUST MANTLE Pacific Ocean Puget Sound TA CHECK_________________ Lab #8: Geology of Washington 114 2. What rock type erupted in flows in the Columbia River region about 17 million years ago? ______________ __________________________________________________________________________________________ 3. Does this rock type make sense based on our tectonic setting? What type of volcanic rock or magma usually forms in a continental-oceanic subduction zone such as ours? Explain. __________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 4. According to the lab manual, what is a possible explanation for the eruptions of mafic magma that formed 17 million years ago in the Columbia River region? __________________________________________________ __________________________________________________________________________________________ Activity 2: Cross-Section of Washington In this activity you will use the geographical locations provided by your flip book, as well as the historical order of events from Activity 1, to create a cross-section of Washington. 1. Fill in the blanks for each terrane, volcanic arc, or depositional basin using the names in your lab manual. Think of the geographic distribution on your map and principles of relative dating when making decisions about where each piece belongs.
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TA CHECK_________________ Lab #8: Geology of Washington 115 Activity 3: Rocks of Washington This activity will provide an excellent review of the rocks for the final exam as well as helping you learn to recognize the rocks you will see around our state. Each tray of rocks you identify will represent the rocks found in one of the terranes, arcs, basin or other geologic features of Washington. For each tray, identify each of the
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